In the case in which a receiving operation is to be carried out in a code division multiplex communication, a receiving device has a structure shown in FIG. 28. The receiving device has an AD converting portion 1501, a reverse diffusing portion 1502, a synchronous detecting portion 1503, a weighting portion 1504, a rake synthesizing portion 1505, a channel decoding portion 1506, and an error correcting portion 1507.
Receive data 1500 are digitized by the AD converting portion 1501, are subjected to a reverse diffusion processing in the reverse diffusing portion 1502, are synchronously detected by the synchronous detecting portion 1503 to carry out a phase adjustment through the phasing of a receiving signal, and are then rake synthesized by the rake synthesizing portion 1505 and are thereafter channel decoded by the channel decoding portion 1506, and furthermore, are error corrected by the error correcting portion 1507 and are output as decode data 1508.
The synchronous detection in the synchronous detecting portion 1503 is often carried out by a method such as an interpolation. As shown in FIG. 29, in the interpolating synchronous detection, a shift of a frequency of a carrier signal from a transmitting device side and the amount of a phase rotation by phasing are obtained by using front and rear pilot symbols on a time basis for the receiving symbol, thereby calculating a phase estimation value.
In this case, a rear receiving signal on a time basis is used. Therefore, it is necessary to store the symbol of a synchronous detected channel other than a pilot symbol for a phase estimation and to calculate the phase estimation value, thereafter carrying out the synchronous detection.
In the code division multiplex communication, in order to reduce a data volume to be stored, there is generally taken a method of digitizing receive data by an AD converting portion 1401 and reversely diffusing the same data by reverse diffusing portions 1402, 1407, 1413 and 1419, and then storing the symbol of a synchronous detected channel other than a pilot symbol for a phase estimation by memories 1404, 1408, 1415 and 1420 (see Patent Document 1). In FIG. 22, 1403, 1409, 1414 and 1421 denote a phase estimating portion, 1405, 1410, 1416 and 1422 denote a synchronous detecting portion, and 1406, 1411, 1417 and 1423 denote a weighting portion.
(Patent Document 1) JP-A-2002-171200 Publication (FIG. 7)
However, a standard for receiving a large number of channels diffused and modulated by using different diffusion codes at the same time to enhance a communication speed has appeared by a need for a high-speed data communication. Accordingly, there is a problem in that a large number of reverse diffusing portions for receiving a plurality of channels at the same time and a large number of arithmetic unit resources for a synchronous detection are required and the amount of receive data subjected to the reverse diffusion is increased. This causes an increase in the scale of a circuit.
On the other hand, it is advantageous to store symbol data obtained after the reverse diffusion in order to enhance the use efficiency of a memory and to reduce memories to be mounted on the receiving device depending on the quantity of a symbol rate or a multipass in some cases.
There will be described a specific example of a reduction in the memories to be mounted. In a CDMA communication, symbol data received for carrying out a synchronous detection and rake synthesis are to be stored for a constant section every multipass. In the CDMA communication, in the case in which a diffusion rate is high, a data size can be reduced by an integral calculation to be carried out in the reverse diffusion. In a recent high-speed data communicating method having a low diffusion rate, a diffusion rate is low (for example, 4) and a larger memory space than original receive data is used in consideration of the storage of data corresponding to a multipass in some cases.
FIG. 31 shows a specific example. In case of an 8-bit input, a 256-time diffusion and 12 multipasses, 8 kB receive data can be stored in a capacity of approximately 0.8 kB after the reverse diffusion, which is efficient. In case of a 4-time diffusion and 12 multipasses, a capacity of 33 kB is required after the reverse diffusion so that the efficiency of the data storage is low. Therefore, it is preferable that the 8-bit input signal should be stored before the reverse diffusion and the reverse diffusion and synchronous detecting processings should be executed when data for a desirable section which is required for the synchronous detection can be stored.
The reverse diffusing portion requires a real-time processing for the receive data so that it is hard to carry out sharing on a circuit resource basis and a change into dedicated hardware is indispensable. For this reason, there has been demanded an enhancement in a degree of freedom of a processing timing in the reverse diffusion processing during the simultaneous receipt of a large number of channels.
It is an object of the invention to provide a receiving device capable of reducing a storage memory when receiving a large number of channels at the same time and enhancing a degree of freedom of a processing timing in a reverse diffusion processing.